To address the increasingly demanding workloads, processor sockets are added in a seamless way within a single server. You’re scaling up. Sockets are connected together as well as the memory and IO boards and applications can benefit from more compute power.

What’s the issue with the Intel QPI source broadcast snoopy protocol? To achieve cache coherency, a read request must be reflected to all processor caches as a snoop. You can compare this as doing a broadcast on an IP network. Each processor must check for the requested memory line and provide the data if it has the most up to date version. In case the latest version is available in another cache, source broadcast snoopy protocol provides the minimum latency when memory line is copied from one cache to the next. In a source broadcast snoopy protocol, all reads result in snoops to all other caches consuming link and cache bandwidth as these snoop packets use cache cycle and link resources otherwise used for data transfers.

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About PiroNet

Didier Pironet is an independent blogger and freelancer with +15 years of IT industry experience.
Didier is also a former VMware inc. employee where he specialised in Datacenter and Cloud Infrastructure products as well as Infrastructure, Operations and IT Business Management products.
Didier is passionate about technologies and he is found to be a creative and a visionary thinker, expressing with passion and excitement, hopefully inspiring and enrolling people to innovation and change.

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